There is an increasing demand for wire ropes in spatial structure, large stadiums, tourism cableway, deep winding and other applications. This requires high stranding quality, structure and performance of the wire ropes at the same time. At present, single strand rope of circular steel wires is generally produced. During its use, such single strand rope is subjected to both a primary bending stress from the external circular objects such as a pulley or a reel and a secondary bending stress due to severe squeezing caused by excessive slippage of steel wires between layers of the rope. In a worse case, if a structure of an inner layer of the ropes is relatively loose, a tertiary bending stress may occur. A surface of the rope is not in complete surface contact with the external circular objects, so that the compressive stress is uneven and bending stresses increase. This leads to poor fatigue resistance. At the same time, single strand rope has a small filling factor, low breaking force, short service life and large usage limitations so it can hardly meet actual needs.
In addition, the existing 8/1000 closer does not have enough plant capacity, for it has only eight spools used for manufacturing the steel wire ropes. A locked coil wire rope with a diameter of 80 mm requires at least 40 steel wires in outermost layer and consequently at least 40 spools. So the existing closer is far from meeting the demands for large-diameter steel wire ropes with over 40 steel wires in the outermost layer. Large-diameter locked coil wire ropes with over 100 steel wires and with no more than eight steel wires in the outermost layer can only adopt eight spools to strand at least 12 times of repeated stranding. This leads to extremely low production efficiency. Due to different diameters between the inner layer steel wires and outer layer steel wires in the structural designs, different spools are needed for adaptation. It is impossible for the single 8/1000 closer to finish the production practically. Actually, the locked coil wire ropes with a diameter larger than 80 mm require at least 100 steel wires in total.